This feature allows a card number, its date expiry and CCV number to be validated on the client-side (on client’s browser) before they are sent to the Braintree gateway. By doing this there are eliminated the unnecessary round-trips to the Braintree gateway just to find out later that the card number is invalid or its date is already expired. If a field is not valid then the user will notice (1) a field shake while trying to submit the order and (2) the field gets focus and the checkout form is not submitted.
By validating the card number the plug-in does not check if the card number is a real card number issued by a real card company or not. Instead it checks if the card number respects a certain numbering pattern made public by its issuing company. The same for the CCV. As for the expiry date it is only verified if the date is before the current date or not.
The following cards are supported: VISA, American Express, JCB, MasterCard, Maestro, Diners Club and Discover.